What is the purpose of ‘explain’ in PostgreSQL?

In PostgreSQL, the EXPLAIN statement is used to analyze the execution plan of a query, helping developers and database administrators understand how the system executes a specific query and optimize query performance.

When you run a query, you can add the EXPLAIN keyword before the query to obtain the query execution plan generated by the PostgreSQL optimizer. The execution plan is a tree structure that displays each step of the query and their order of execution, tables involved, indexes used, and other information.

By analyzing the execution plan, you can identify potential performance bottlenecks, understand the optimization strategies of the query optimizer, and try to improve the performance of the query. Typically, you can see which indexes are being used, which sorting operations are being performed, the types of connections, and other key information.

In conclusion, the EXPLAIN statement in PostgreSQL helps you understand the execution plan of a query, allowing you to optimize query performance.